Revealing mistake: (Part 4) After Omega takes off his mask and looks in the mirror, when he sees that his physical body doesn't exist he puts his mask back on and screams, but when he shouts, "If I exist only by my will, then my will is to destroy," Omega's mask pops up off his face, and we can see the actor's blackened face as he shouts the last bit of his dialogue.

Plot hole: The Brigadier says UNIT HQ is 'a Top Secret establishment'. It is, in fact, so secret that it has a large sign outside informing the world not only of its function, but also the name of the commanding officer.

Continuity mistake: At the end of episode one, when the Doctor and Taron spray paint onto the invisible Dalek, they use two different colors. At the start of episode two, the Dalek is suddenly black and painted on all sides.

Revealing mistake: When the Doctor and Jo see Bessie in the middle of the rocky area, there is the white chalky substance from the ground on her wheels, indicating she was driven to the spot rather than being "transported" to the black-hole.

Visible crew/equipment: (Ep. 2) When the Doctor, Jo, and Dr. Tyler are taken into Omega's palace, in the first shot of the multiple passageways (right before Jo says that it looks like Aladdin's cave) the curved chalk actor's mark can be seen on the floor, which can be seen again in three following shots. Note that when they're all escorted further inside, just as Dr. Tyler comments about the matter/anti-matter not making sense, Jon Pertwee can be seen looking down, presumably to make sure he hits his mark.

Revealing mistake: In episode 3, when the second Doctor, the Brigadier and Benton emerge from the TARDIS, the doors are left completely open with the camera looking straight into them for a long time, revealing not only the emptiness of the police box shell, but also that there's a pair of secret doors on the opposite side to the entrance doors. These 'secret doors' come in handy during episode 4, allowing seven people to come out of the police box in the final confrontation with Omega. (Well, it is stated time and again that the TARDIS is "bigger on the inside than the outside". Now we know how that happens...).

Visible crew/equipment: At various points in the story, the pots for the plants of the Spiridon jungle are visible. Episode two has a couple of noticeable moments, when Codal is captured and when the Doctor is led away by the Daleks.

Revealing mistake: At various times (especially in episodes 3 and 4) you can see actor Stephen Thorne's lips through Omega's mask (and in one profile shot you can also see his jaw), yet when his mask is removed, we find that Omega has been dissipated and has no face...

Continuity mistake: In episode five, Jo's hairstyle changes. She has one hairstyle in the bulk of the episode, which was filmed in the studio. And a different one during the "Plain of Stones" scenes, which were shot on location.

Revealing mistake: When Benton jumps over the maggots to get into the cave the Professor and Jo are hiding in, the jump causes the floor to move, giving away the fact that the floor is wood covered by a small amount of gravel.

Continuity mistake: In the very first scene of the story, Jo is holding a gun as she opens the TARDIS doors, but when they come into the console room, she has no gun and is using both hands to support the Doctor.

Other mistake: The end titles of episodes 2, 5, and 6 of "The Green Death" were run backwards and upside-down. According to some published accounts, this was due to the telecine operator forgetting to rewind the end title film sequence before playback.

Audio problem: When the companions are returning to Earth via the pillar of smoke, you can see and hear each person walk up the steps and then supposedly disappear. Unfortunately, you can then hear them walk down the other side of the steps..

Other mistake: Near the end of episode 5, Stevens is reading out previous numbers of slave units and B.O.S.S is telling him the new ones. For New York, the previous figure was 7203 and the new figure 7580. However, for Moscow the previous figure was 10003 (ten thousand and three), and the new figure is 110098 (one hundred and ten thousand and ninety-eight), which is a big difference.

Continuity mistake: (End of Ep. 3 and start of Ep. 4) When the Third Doctor fights the dark side of Omega's mind, the rings that the Doctor wears on the pinky fingers of both hands switch to his ring fingers, then back again to his pinky fingers, between shots. Then as Omega chokes the Doctor, the ring on his right pinky vanishes between shots.

Factual error: When the inside of an apple is exposed to the air for about fifteen minutes it oxidises and goes brown, but Jo's breakfast apple goes brown by the end of the scene. (This is assuming she wasn't deliberately eating a brown apple).

Audio problem: In Part 3 when the Brigadier gets behind the sand pile with Arthur Ollis, the Brigadier asks him "Did you find a way in?" This is not Nicholas Courtney's voice for this one line. He speaks again right after that and it is his voice.

Visible crew/equipment: (Part 3) After Omega has revealed himself to the Third Doctor, Jo, and Dr. Tyler, when he begins to speak privately to the Doctor the camera casts a shadow on Omega's body. Then after Omega turns around the boom mic dips into view at the top of the screen. And when Omega starts walking forward, the shadow of equipment (presumably the boom and mic) can be seen moving on the far wall, near the lower left of the screen.

New this monthSuggested correction:Basic lifecycle of extremely massive stars: they're born, they live for several million years, they die in a large supernova. There are two potential outcomes of a supernova: the creation of a pulsar or neutron star, or the creation of a black hole, depending on how massive the original star was. So yes, black holes are indeed created in supernovas.